Cellulose derivative compositions



Patented Apr. 9, 1940 PATENT OFFICE 2,196,575 I CELLULOSE DERIVATIVEcomosrrions Shailer L. Bass, Midland, Mich, and Earl G.

Hallonquist, Shelton,

Wash, assignors to The DowChemical Company, Midland, Mich, a corporationof Michigan No Drawing. Application August 4, 1988,

1 Serial No. 222,994

5 Claims. ,(01. 106-40) This invention relates to' compositions ofmatter comprising solvent-soluble derivatives of cellulose andpoly-chlorinated diaryl ethers.

In preparing a plasticized cellulose derivative 5 composition, it isordinarily the object to provide a composition which is more flexiblethan the original unplasticized cellulose derivative. Flexibility,however, is not the only desirable .attribute of a cellulose derivativecomposition and the selection of a plasticizer which will modify variousother properties of the said cellulose derivative requires considerablecare and experimentatlon. Among the properties of the cellulosederivatives which it may be desirable to modify are those of moisturepermeability which should ordinarily be reduced, flexibility whichshould be increased, tensile strength which should not be decreasedmaterially .and if possible should be increased, and for certainpurposes the flammability characteristics and dielectric propertiesshould each be modified so as to make the cellulose derivativesubstantially nonflammable under the conditions of its use and convertedto a product satisfactory for use as an electrical insulating medium.

Numerous plasticizers are known which soften cellulose derivativessufliciently so that they may be employed in the form of flexible foil,sheets, or tape, as wrapping material or the like. Compositionscomprising such of the customary plasticizers, for example, as dibutylphthalate or tricresyl phosphate, are ordinarily not materially betterthan the cellulose derivative alone as regards moisture permeability,flammability, or

dielectric properties. Hence, such compositions cannot be employedsatisfactorily as electrical insulating media around wires, cables, andthe like, where moisture permeability and flammability of the insulatingcomposition are as im-- portant as the flexibility and dielectricproperties.

It is accordingly an object of the present invention to providecellulose derivative composi-' I I tions comprising plasticizers whichwill improve the flexibility, reduce the moisture permeability,

- suppress or overcome the tendency of the cellulose derivative towardflammability and improve the dielectric properties. It is a furtherobject of the invention to providea cellulose derivativev compositioncomprising a plasticizer which will 5 accomplish the foregoing ends andat the same time increase the tensile strength of the said cellulosederivative when' employed under certain hereinafter specifiedconditions. Other objects of the invention and advantages accruing 1othereto will become apparent as the description proceeds.

The solvent-soluble derivatives of cellulose with which the invention isconcerned are the" cellulose ethers, cellulose esters, and nitro-cellu-16' lose. The cellulose ethers which we employ according to thehereinafter described invention are the water-insoluble alkvl andaralkyl ethers of cellulose. i. e. those containing from about 2.0'toabout 2.75, or higher, substituent groups 20 per anhydro-glucose unit.Examples of such ethers are the water-insoluble ethyl, propyl, butyl,lauryl, and benzyl ethers of cellulose and mixed cellulose etherscomprising a plurality of these substituent groups. The cellulose estersas which we may employ include cellulose acetate, cellulose propionate,cellulose butyrate, cellulose acetate-butyrate, celluloseacetate-propionate, and the like. Nitrocellulose, in its variouscommercially available viscosity types is also included in theexpression "solventsoluble derivative of cellulose as employed herein inthe description and claims.

We, have now found that the aforementioned desirable ends may beattained by incorporating in a solvent-soluble derivative of cellulosefromabout .01 to about 1.0 part, per part of the cellulose derivative,of a polychloro-diaryl ether. The polychloro-diaryl ethers which weprefer to employ are those comprising from 3 to '7, and preid0 erablyfrom 5 to 6, .chlorine atoms substituted in one or more of the aryl'nuclei of the'said ether. We prefer to use those chlorinated diarylethers which are viscous liquids or low-melting solids. When such etherscontain the number d5 of chlorine atoms d above,

have. ingeneraLflashpointsinexcessotZOO' O. and

do not support combustion. Specific examples of the chlorinated diaryletherswhlch we may employ are the 131-. tetra-, penta-, heza-, and

heptachloro-diphenyloxldes and the correspondingly chlorinated phenyldiphenyloxides. The chlorinated phenyl' naphthyl and dinaphthyl ether-smay be similary employed. The flash v point of these materials is veryhigh and none of them have a fire point or will support combustion.Furthermore, the chlorinated aryl ethers are good solvents for thecellulom derivatives, thus increasing the plastic flow oi. compositionscontaining the same, during molding.

We have found that when from 1 to 5 per cent of the aforesaid 'type ofplasticizer is incorporated in a solvent-soluble derivative of cellulosethe-resulting composition is characterized by its ability to depositfilms which have greater tenslle strength than the untreated cellulosederiv- "ative. These films have slightly improved waterimpermeabilityand considerably better flexibility than do the orignaluntreatedcellulose derivatives. When from .05 to 1.0, and preferablyirom .15 to .40 part of plasticizer, per part of cellulose derivative,is incorporated in the compositlon, there is a substantial reduction oithe moisture permeability, an increase in the dielectric strength, andthe softened cellulose derivative is much less susceptible to combustionthan was the unplasticized compound. In fact, when a flame and thenremoved. Unplasticized celluthe solvent-soluble cellulose derivativesare mixed 7 with to per cent of their weight of a polychloro-diarylether, foils prepared therefrom iail to support combustion when heldhorizontally in lose derivatives and those plasticized with many enJIsItIS'C- centsolutionthereotinasolventconsisting 1 commonplasticizers under like test conditions burn with little dimcult'y. Wehave. found that the improved electrical properties of our compositionsare retained whenthe composition is aged, as indicated by exposuretests, eitherioraperiodotaboutoneweekat 70 C. or for about three weeksexposed during daylight hours to'dlrect sunlight.

The following examples will illustrate the practice oiour invention: l V

name! An etlwi cellulose havlngahout 48 ethoxyl content and a vlscmityof 5 per 'sultingcompositions whmcastintofllms was determined. Theresults are given in the following table:

percent W M e m 1a Do -21: 40 no as H loxide.- is no 21 Do. 40 356' 25:None Q1 12 groupspermolecularunitwastestedin Pengadiloro-dlphenyloaideun ufloxghhfidifibenyloiide: V 0

Benzyl cellulose containing about 2.5 benzyl a like manner. The resultsare asfollows: a

' Table 2 Elo Plastieizcr nga 7 per cent Pe11Dh:hloto-diphcny1ofidc-lHerlchlormdlno E rf TEESIIIIII None a cacti Exuumx 3 A sample ofcellulose acetate-butyrate similarly plasticized gave the followingresults:

more a Elongation Plastieizer per cent Am I;

quanta- Nam EXAITIJQ' alLsomewhat sotterthantheorizinal unpla'stlcinedmaterials. butas issceniromthetables did not great a mum oftheir-original tensile strength to make them unsuited tocommercialmeaswrapplnamata'lalsandthe like. a

As is to'be oi plasticizers save thestrungerfllms. 4

Following the favorable hidications as to Plasticity. tensile strength;and elongation ob-.

talned from the experiments reportedabove,iurtherweremade toascertaintheeiiectot the herein-described plasticizers on the moisturepermeability and dielectric properties otva'rious cellulose derivatives.The iollowing tables set-forth the results of these tests as regards theuse of he'xachloro-diphenyloxide as the plasticizer. In all experimentswhere a plasticizer was employed; it was used in an amount equal to 15percent of the weight ofthe particular cellulose derivative,

In a like manner cellulose acetateepropionate dioxane, by volume, wasadded on cellulose acetate and 15 per cent oihexachloro-'diphenyloxide,- cf. runs 9 and 10 of the preceding table, asample of the same cellulose acetate'was plastlcized with 15 per cent or,diphenyloxide'itself. The plasticized material had a moisturepermeability of 1410 grams per square meter per 24 hours, a tensilestrength of only 540 kilograms persquare centimeter, and an elongation01' 5.8 per cent. From the foregoing Table 5, it is observed that ethylcellulose of standard ethoxyl content, 1. e. from about 45 to 49 percent, and or any .viscosity type is materially improved as to moistureimpermeability and is not materially effected as to tensile strength bythe incorporation o! 15 per cent of hexachloro-diphenyloxide. In someinstances, in fact, the tensile strength of the plasticized product isactually higher than that oi. the original unplasticized material.Similar results ,are reported in the tables for cellulose acetate and 6-second nitrocellulose. The moisturetransmlse sion is much lower than inthe unplastlcized cellulose derivatives and compositions comprisingtricresyl phosphate, dibutyl phthalate. or. castor oil as-theplasticizer. For under-water service, however, water-proofing agentswill be required.

Electrical properties of the same compositions preceding Table 5indicate a marked improvement of the plasticized compositions over theoriginal implasticized cellulose derivatives. The dielectric strength,volts per mil, of representative ethyl celluloseand cellulose acetatesamples are reported in Table 6,

as reported in the wherein the run numbers correspond tothe-compositions of similar number in Table 5.

lower than that of many additional liable 5Eflectoi'flingcnfilmproperties am; 061mm Visc Moist an n; imrsnmc 17d x01 m can; ay sun ight No. derivative g no; cps. aria/m3}; hrs.

' '1. I. Tenant T.'S. Pcccnt 'l. 8. Percent kgJcmJ clong. izgJcm. along.kgJcm. I along.

1 Ethyl cellulose 45.4 44 1270 44!) 4 M 5 480 7 2 do 15 1110 a 460 d 4156 475 6 3 "do 0 41.0 15 mo; 440 8 475 10 445 ll do 16 10 450 11 450 10430 11 5.----- do 0 41.8 22 15H) 4m 12 can 16 am 6.----- do l5 M 485 294M 26 450 21 7 do 0 49.4 19 ms 510 23 M 25 470 23 R y 15 a 870 806 16 Tmk 26 T& k 23 9 Oclluloseacetatc 0 172) 740 4 am w s) 7 120 wee 58 10 anl5 842 710 5 s70, 4 870 3 11... Base. nitrocellulose" 0 m 700 24 m 10730 12.8 12 do a l5 212 770 22 1000 15 700 4 By way of contrast with theresults obtained occurred. A film was cast from the so-formed solutionwhich,-when freed from solvent, had a tensile strength of 478 kilogramsper square centimeter of original cross section. The ethyl cellulosefrom which this composition had been prepared could be cast into filmshaving an average tensile strength of only 440 kilograms per squarecentimeter. The addition or 2 per cent by weight ofpentachloro-diphenyloxide resulted inran 8.7 per cent increase intensile strength. i

.A solution of ethylcellulose, identical with that employed in hepreceding example, was treated with 4 per cent by weight ofpentacbloro-diphenyloxide based on the weight of ethyl cellulosepresent, Films cast from this solution had an averagetensile strength2.3 per cent greater than that of the untreated ethyl cellulose.

when 6 and 8 per cent, respectively, of pentachloro-diphenyloxide wereadded-to portions of this same ethyl cellulose solution, films andfilaments produced therefrom had an average tensile str'ength 1.3 and2.3 per cent lower than that of the untreated ethyl cellulose, but hadimproved electrical properties and were noticeably resistant tocombustion.

Emu: 7

An' ethyl cellulose capable of forming films, filaments, and the like,having an average tensile strength of 424 kilograms per squarecentimeter of original cross section was treated with 5 per cent byweight of. pentachloro-diphenyloxide. A solvent-free product from theso-treated solution exhibited an average tensile strength of 4'73kilograms per square centimeter,

Tobie 6.Dielectric strength, voltsper mil Noezins lweek at70C.lldaysinsun Sweeksst'lO o. Sweeksinsnn A iii A er l5 Aver i5 Aver 0S5Avcr m V8120 V .0 .0 samples High Low gamma High Low High Low mp HighLow 88mm High Low 2100 saw 2200 11cc 21cc 1500 as me am sacs m 1800 90031m 5000 2100 nso 1am an 680 0st 417 as e82 304 1350 men 1350 1190 20901470 sso mes as Enema 5 I increase of 11.5 per cent in the tensilestrength.

To 300 grams or a 12 per cent solution or ethyl cellulose in 'a solventconsisting of 48 parts of benzene, 12 parts of'ethanol,

0.72 gram (2 per cent by weight) of pentachloro-diphenyloxide.

The mixture was stirred until complete solution and parts or When 10 percent of pentachloi' o-diphenyloxide was added to a solution of this sameethyl celluincorporated in the ethyl.

representing an poly-chlorinated diaryl ethers may be similarly.

were only 16.5 per cent less strong than the untreated material, and hadthe improved flexiproportions of plasticizer, i. e. from .05 to 1.0

part per part of cellulose derivative, improve other properties ashereinbeiore disclosed. The same in general is true forhexachioro-diphenyloxide, tetrachloro-diphenyloxide, and otherpolyhalo-diaryl ethers.

The types of ethyl cellulose to which the chlorinated diaryl ethers maybe added with ad vantage are those having ethoxyl contents ranging fromabout 42 per cent to about 50 per cent. Those with ethoxyl content inthe lower portion of this range are adapted to the preparation of moldedplastics and the like, while those having from about 48-49 percentethoxyl are the ones best adapted to the preparation films and strongflexible fibers.

The invention has been discussed with reference. to the use of thechlorinated diphenyloxides as the plasticizers for cellulosederivatives. The chlorinated phenyl-diphenyloxides and other employed,and with similar eflect upon tensile strength, flexibility, moistureimpermeability, re!

sistance to flammability, and dielectric strength.

The compositions may be employed as'electrical insulating wrapping forcables and the like, or in coating compositions where the abovelistedimproved properties are desirable, especially in the fabrication ofrelatively nonfiammable articles. The compositions may also be used inthe extrusion coating of wire. Solid electrical insulators may be madeby molding the herein described compositions into suitable shapes. a

Other modes of applying the principle of our invention may be employedinstead of thoseexplained, change being made as regards the materials orprocess employed, provided the ingredients stated by any of thefollowing claims or the equivalent of such stated ingredients beemployed.

of transparent We therefore particularly point out and distinctly claimas our invention:

1. A composition of matter comprising a cellulose ether containingbetween about 2.0 and about 2.75 etheriiying roups peranhydro-glucoseunit, plasticized with between about .01 and about 1.0 part by weight 01a polychloro-diaryl oxide containing between about 3 and about chlorineatoms substituted in the aryl nuclei per part of said cellulose ether,to improve the flexibility, reduce the moisture permeability andflammability, and increase the dielectric strength of the said celluloseether.

7 2. A composition of matter comprising a cellulo'se ether and betweenabout .05 and about 1.0 port by weight of a polychloro-diaryloxidecontaining between about 3 and about 7 chlorine atoms substituted inthearyl nuclei per part of said cellulose derivative, to improve theflexibility,

reduce the moisture permeability and flammability, and increase thedielectric strength of the said cellulose derivative.

3. A composition of matter comprising a cellulose ether and betweenabout 15 and about 40 per cent of a polychloro-diaryloxide containingbetween about 3 and about 7 chlorine atoms substituted in the arylnuclei based on the weight of said cellulose derivative, to improve theflexibility, reduce the moisture permeability and flammability, andincrease the dielectric strength of the said cellulose-derivative. I

4. A composition of matter comprising ethyl cellulose containing betweenabout 42 and about 50 per cent ethoxyl groups, plasticized with betweenabout .05 and about 1.0 part by weight of a polychloro-diphenyloxidecontaining between about 3 and about 7 chlorine atoms substituted in thephenyl nuclei, to increase the flexibility,

reduce the moisture permeability and the flammability, and increase thedielectric strength of the said ethyl cellulose.

5. A composition of matter comprising ethyl cellulose plasticized withbetween about 15 and about 40 per cent of hexachloro-diphenyloxida toincrease the flexibility, reduce the moisture permeability and theflammability, and increase the dielectric strength of the said ethylcellulose.

BHAILER L. BASS. EARL G. HALLONQUIST.

so I

